Flight recorder

An airplane’s Flight Data Recorder is known as the “Black Box.”

The Flight Data Recorder was invented by an Australian named Dr David Warren. The original model was red, although these days they are usually orange to make them easier to find. A journalist at the launch described it as a “wonderful black box” to make the point that how it worked was complex and one didn’t really need to know, but that it worked was the important thing.

The phrase has since been commonly used to indicate a mystery that the user of the phrase does not understand.